1. Field of the Invention
The present invention relates to a device for sampling and/or injecting fluids whose composition is liable to evolve reversibly under the effect of a change for example, in a thermodynamic parameter.
Various devices for sampling a fluid under analysis are described in the prior art.
2. Description of the Prior Art
One example of a device according to the prior art is shown in FIGS. 1, 1A, and 1B. It enables a sample of gaseous, liquid, or multiphase fluid composed of several phases of different natures to be sampled from a treatment unit so that a chemical or physicochemical analysis of this sample can be performed. The sampling device comprises a chamber 1 initially filled with liquid mercury, the mercury being expelled through orifice 2 when the chamber is filled with liquid entering through orifice 3 (FIG. 1A).
When sampling is complete (FIG. 1B), orifices 2 and 3 are closed by valves or stopcocks 4, and the device containing the sample is transported to the analysis device. During this transportation, the thermodynamic conditions may change, and it becomes necessary to restore the fluid sample to a state substantially identical to its initial state to obtain a representative analysis. For example, if the sample has at least partially vaporeeed during the sampling operation, an attempt is made to restore the sample to an essentially liquid state corresponding essentially to its original state by injecting a given quantity of mercury through orifice 3, opening 2 being closed. The phase that vaporizes is then recompressed and is converted into a liquid phase.
It is also possible to monitor and restore the temperature conditions when the rheological behavior of the fluid sample is to be studied, for example by placing this device in an oven.
While such a device does allow the fluid to be kept in or restored to its initial state to overcome the sampling conditions and thus obtain representative analysis results, it has nonetheless the drawback of using mercury which is a harmful product which, when placed in direct contact with the fluid sample, can interact with the latter and alter its nature.
Another procedure described in the prior art consists of analyzing the fluid without restoring it to its initial state by analyzing the liquid and vapor phases separately, then correcting the results obtained by calculating the liquid-vapor balance, taking into account the compositions of each of the phases to determine the state of the sample corresponding to given sampling conditions.
Such a method is effective but may be complex and slow.